do not ignore errors in man subdirs

If an error occurs in a man subdir, make sure we propagate it back up.

While we're here, merge the duplicate rules into one.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

man/Makefile

@@ -4,17 +4,11 @@ INSTALLMAN=install -m 0644
 
 SUBDIRS = man3 man7 man8
 
-all:
-	@for subdir in $(SUBDIRS); do $(MAKE) -C $$subdir; done
+all clean install:
+	@for subdir in $(SUBDIRS); do $(MAKE) -C $$subdir $@ || exit $$?; done
 
 distclean: clean
 
-clean:
-	@for subdir in $(SUBDIRS); do $(MAKE) -C $$subdir clean; done
-
-install:
-	@for subdir in $(SUBDIRS); do $(MAKE) -C $$subdir install; done
-
 .PHONY: install clean distclean
 
 .EXPORT_ALL_VARIABLES: